Heating apparatus



M 1946- H. B. HOLTHOUSE 7 2,400,116

HEATING APPARATUS Filed March 25, 1942 s Sheets-Sheet 1 y 1946- H. B. HoL'rHousE 2,400,116

HEATING APPARATUS Filed March 23, 1942 3 Sheets-Sheet 2 May 14, 1946. Y H. B. HOLTHOUSE HEATING APPARATUS 5 Sheets-Sheet 5 Filed March 25, 1942 .Patenied May 14, 1946 APPARATUS Harry Brlioltliousc,- Chicago, IlI.,-asslgnor to Galvin Manufacturing Corporation, Chicago,

Y 111;, a corporation Illinois Application March 23. 1942, Serial No.435,845 12 Claims. (01. 126-116) This invention relates generally to heater apparatus and in particular to heater apparatus 0i internal combustion'type adapted to operate over a wide range of altitudes in which the atmosphere varies in pressure and oxygen content.

Heating devices of internal combustion type are in common use for mobile craft operating at ground temperatureand atmospheric conditions. When used in an aircraft some of these heaters may operate satisfactorily up to altitudes of about 15,000 feet. However, at altitudes from 15,000 feet up to 35,000 feet and more the usual heating devices of the prior art are incapable of operating satisfactorily because of the reduced oxygen content in the rarifled atmospheres at high altitudes and the cold temperatures encountered at such high altitudes.

It is an object of this invention, therefore, to

operate over a wide range of altitudes in which the air and fuel supplied for combustion is simultaneously varied by barometric pressure operated provide an improved heating device of internal.

combustion type.

Another object of this invention is to provide a heater adapted for operation over a wide range of altitudes where the oxygen content of the com bustion supporting medium supplied to the heater for combustion varies widely, having means for maintaining the combustion supporting medium substantially uniform in combustibility while the heater is being operated over such wide range of altitudes.

. Yet another object of this invention is to provide air moving apparatus which maintains a substantially constant supply of oxygen over a wide range of altitudes.

A further object of this invention is to provide a heater device in which the air and fuel for combustion are mixed together'in the presence of heat so asto entirely eliminate any rela tive cooling efiects between the air and fuel.

Another object of this invention is to provide heater apparatus which is simple and compact in construction, light in weight, and capable of operating efficiently and positively over a wide ,range of altitudes in which the atmosphere varies in pressure and oxygen content.

A further object is to provide a heater in which the air for combustion is automatically increased as its oxygen content decreases.

Yet another object of this invention is to provide heater apparatus having a combustion chamber in which the oxygen supplied to the combustion chamber, and the pressure in the combustion chamber are maintained substantially constant over a wide range of altitudes.

A feature of this invention is found in the provision of a heater of internal combustion type including air moving means supplying air, for

combustion having an inlet adjustable in response to atmospheric pressures.

Yet another feature of this invention is found in the provision of. heater apparatus adapted to means to maintain the air and fuel mixture substantially uniform at all altitudes.

A further feature of this invention is found in the provision of heater apparatus for high altitude operation in-which electric means for operating air moving means is automatically increased in speed to increase the rate of operation of such moving means in response to pressure actuated means.

Further objects,.features, and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view otheater apparatus showing the assembly therewith of mean providing for its operation over a wide range of altitudes, thecombustion chamber being shown in development for the purpose of clarity;

Fig. 2 is an elevational view of the apparatus in Fig.1 as seen along the line 2-2 in Fig. 1;

Fig. 3 illustrates diagrammatically a control circuit for the apparatus of Fig. l;

Fig. 4 is a sectional view of the combustion chamber as seen along the line 4-4 in Fig. 1; Fig. 5 is a fragmentary plan view illustrated similarly to Fig. 1 showing means operatively associated with the outlet of the combustion chamber for automatically controlling the admission of air thereto; ,j

Fig. 6 is a fragmentary plan view'illustrated similarly to Fig. 1 showing means at both. the inlet and the outlet of the combustion chamber for automatically controlling combustion conditions; and

Fig. '7 is a modified form of the invention showing manually operated means for controlling the admission of air into the combustion chamber.

In practicing this invention there is provided heater apparatus of internal combustion type for space heating in an aircraft. The heater includes a combustion chamber operatively associated with an air and fuel conditioning unit having heating means for heating the same to at least a fuel vaporizing temperature to mix together the air and fuel therein. The air to be heated is directed through a passage in thermotor. The admission of air to the heated air' passage and to the conditioning unit is controlled by adjustable damper means operated in accordance with the altitude at which the aircraft is flying. Since the atmosphere becomes more rare and reduced in oxygen content with an increase in altitude, the damper means are operated to permit more air to be moved by the air moving means with an increase in altitude so as to maintain the supply of oxygen to the conditioning unit substantially constant, and the rate of carrying away the heat from the combustion chamber substantially uniform. The increase in the quantity of air at high altitudes as controlled by the damper means is augmented by means operated concurrently with the damper means to increase the speed of the motor with an increase in altitude. In those instances -where it might be necessary to vary the fuel'supply to the conditioning unit to maintain a substantially uniform air and fuel mixture at all altitudes, there is provided further means for varying the fuel supply concurrently with the air supply after some predetermined altitude has been reached in which a variable fuel feed is desired. All of the above noted means for varying the air and fuel to compensate for the changes in the pressure and oxygen content in the atmospheres at high altitudes are operatively assembled with the heater apparatus to provide in all a compact unit adapted for package handling.

Referring to Fig. 1 of the drawings the heater of this invention is seen to include a housing it) which is divided longitudinally thereof over substantially its entire length by a vertically extending partition member II to provide a mechanical compartment i2 and a heating compartment. Within the heating compartment is a substantially cylindrically shaped combustion chamber 15, shown in development in Fig. 1 for the purpose of clarity, which is closed at one end by a cover plate l3 and at its opposite end by the bottom l4 of a substantially dish-shaped member 20 which defines in part an air supply chamber iii in axial alignment with the combustion chamber [5.

The combustion chamber I5 is divided longitudinally thereof into four axially extending but connected passages Ila-lid by a partition member i8 of substantially X-shape (Figs. 1 and 4). The combustion chamber inlet lfivand outlet 2! are formed in the bottom portion l4 of the dishshaped member 20 in communication with the passages 87a and H11, respectively. Located within the inlet I9 is an air and fuel mixing unit, indicated generally as 22, which is extended within the air supply chamber IS. The outlet 2| is provided with a tail-pipe 23 extended through the air supply chamber l8 and outwardly from the heater at the housing end 24.

The outer wall or body portion of the combustion chamber i6 is provided with angularly spaced axially extending fins 26. The fins 26 have a sleeve 28 positioned about the outer ends thereof to form an annular passage 29 about the combustion chamber l5 for the air to be heated. The air to be heated is admitted into the passage 29 through an inlet 3i connecting the passage with the mechanical compartment i2 and is circulated through the passage 23 by .a fan 32 located within the compartment l2 and mounted on a shaft 33 for an electric motor 34 which is of series wound type. The compartment i2 and air passage 29 are separated from the air supply chamber It by a sealing or partition member 33 extended transversely of the housing II). From Fig. 1 it is seen that the air supply chamber 16 is defined by the member 20, the partition member 36, and the end 24 of the housing i0. Air circulated by the fan 32 is thus confined to travel within the compartment i2 and passage 29 and is discharged from the passage through an outlet 31 which is connected to a space to be heated.

The air supply chamber it receives air from a fan 38 located therein and mounted on the motor shaft 33 which is journalled in the partition plate 36. An inlet 39 for the fan 33 is provided in the housing end 24. It is seen, therefore, that the fans 32 and 38 are operated by the motor 84 and are mounted directly on the shaft 33 thereof. tion of .a fuel pump 4! which is illustrated as being of solenoidtype. The breaker assembly $2 for controlling the energization of the pump 4! is operatively associated with the motor shaft- 33. Fuel for the pumpM is supplied thereto from a suitable source (not shown) through a pipe 43 and is delivered through a pipe Mi to a fuel injection nozzle 48 formed as a part of the air and fuel mixing means 22. The pump dl, motor 34 and fan 32 are thus all located within the mechanical compartment 82, which is provided with an inlet 41 for supplying either fresh or recirculated air to the fan 32 for delivery to the air passage 29.

The air and fuel mixing means 22, previously mentioned, includes a casing member 48 which is closed at one end and open at the end 49 thereof with the passage Ila (Fig. 1). A mixing chamber 5| is located at'the closed end of the casing 43, and is separated from an equalizing chamber 52 by a perforated plate member 53. The equalizing chamber 52 in turn is both defined and separated from the combustion chamber passage ila. by a perforated heat insulating plate 54 spaced inwardly from the end 43 of the casing 48. Extended substantially axially through the casing 48 and supported in the partition plates 53 and 54 and projecting outwardly from the closed end of the casing 48 is a combination electric heating and igniting unit 53 which includes a resistance coil 51 supported in a spaced relation within a metal tube 58.

In the operation of the air and fuel mixing means 22 the fuel delivered to the nozzle 46 by the pump 4i is directed into the mixing chamber 5!, the fuel nozzle. being located within the air supply chamber l8 and mounted directly on the casing 48 at the mixing chamber 5i (Fig. 1). A'portion of the air for mixing with the fuel enters the nozzle 43 from the air chamber it through ports 58 in the fuel nozzle and travels with this fuel into the mixing chamber 5i. Additional air from the air chamber i8 is admitted directly into the mixing chamber 5| through apertures 8! formed in the casing 48 about the fuel injection nozzle 48. The fuel within the mixing chamber 61 is heated to at least a fuel vaporizing temperature by the combination unit 38 to facilitate its thorough mixing with the air. The casing 48, partition plate 53 and tube 58 are provided in a heat conducting material so as to readily receive and conduct the heat radiated by the coil 51. The vaporous air and fuel mixture passes through the perforated plate 53 into the equalizing chamber 52 which in cooperation with the heat insulating plate 54 acts to reduce the turbulence in the mixture and to disperse the mixture substantially uniformly over the entire cross section of the casing 43. This combustible mixture passes through the apertured plate I3 and across the open end 82 of the tube 54 into the effective igniting zone of the combination unit 58 which functions as a heat gun. In other The motor 34 is also utilized in the opera-.

words the heatdeveloped by the coil 81 is proiected outwardly from the open end 82 of the tube 88, the heat generated being dependent upon the watt input to the resistance coil 81. The combustible mixture is thus ignited by virtue of the temperature at the end 82 of thetube 88 being of a degree capable of'igniting such mixture without the mixture itself directly contacting the coil 51. a

The operation of the heater is best understood from Figs. 1 and 3. Admission of fuel to the pump 8| is controlled by a valve unit 88 connected in the supply line 88 and including a valve portion 81. The portion 81 is extended through the unit 88 and has a handle at one end, and is operatively connectedat its opposite end with a control switch 88'. On movement of the valve portion 8'! to a full closing position for the valve unit 88, the switch 88 is operated to an open position so that the pump ll, motor 88, and combination unit 88 are turned ofi concurrently'with from the battery 88 includes conductor 8|, switch 88, terminal-88, conductor 88, a rheostat control arm 80 and a rheostat resistance 88 which'will be later explained, a motor field coil 81, themotor 8|, resistance coil 81, and a ground connection 88.

. The switch 88 includes a switch arm 88 having a brush contact l8! which coacts with the terminals 82 and 88 to separately open and close the pump circuit, and the circuit for the motor and electrical unit 88. Thus, as shown in full lines in Fig. 3 the switch 88 is in an open position which corresponds to a closed position of the fuel valve unit 88. As the valve portion 81 is moved in a counter-clockwise direction, as viewed in Fig.8, to open the fuel line 48 the contact llll initially closes with the terminal 88 to close the circuit for the motor 8| and combination unit 88. As the valve unit 88 continues to be opened the contact [8| while remaining closed with the terminal 88 closes with the terminal 82 to close the pump'circuit. It is seen, therefore, that the operation of the pump 8| is delayed relathe motor 84, resulting from the reduced load on the fans by the decreased density of the air at such altitudes, is sufllcient to compensate for the reduced air density so that a substantially constant supply of oxygen is fed' through theinlet 38 to the mixing means 22 and hence to the combustion chamber l5 to'retain therein a combustion condition which is substantially equal to the combustion condition at ground level. This increase in speed, however, is not great enough to maintain a ground level combustion condition at .altitudes in excess of about 20,000 feet. In order, therefore, to maintain groundlevel heater operation at altitudes above 20,000 feet and up to about 50,000 feet' further compensation for the increase rarification in the air and reduction in oxygen content is provided by means now to be described.

With reference to Fig. 1 the inlet 38 to the air supply chamber I8 is operatively associated with damper means 80 for controlling the passage of air therethrough to the combustion chamber IS. The damper means is illustrated as being of a usual type including louvers 84 connected to a common actuating member 88 for simultaneous movement to open and closed positions relative to the inlet 88. The actuating member 88 is operated by a bellows unit 81 which is responsive to variations in atmospheric pressures to operate the louvers.

' The bellows unit 81 is comprised of mating diaphragms 88 composed 01' a flexible metal or like material forming a closed space having a spring 88- therein acting to push the diaphragms apart. The pressure of the spring 88 i such that at ground level the atmospheric pressure is sumcient to press or squeeze the diaphragms to a closed position. It is readilyapparent, of course, that a closed position of the bellows does not indicate a closed position of the damper means since the louvers 88 are retained partially open at ground level to admit suflicient air into the supply chamber l8 to maintain proper combustion. Further the spring 88 may be calibrated so that the bellows unit 81 is held closed up to an altitude at which a control of the damper means is desired. This is accomplished by setting the spring pressure to correspond to the atmospheric presure at the desired-altitude. As is illustrated tive to the operation of the motor and heating unit 88 sothat a scavenging action is initiated in the combustion chamber l8 prior to the admission of fuel thereto. On closing of the valve unit 88, and in turn moving-of the switch 88 from its dotted to its full line position as shown in Fig. 3, the pump circuit is opened prior to the circuit of the motor and electric heating unit to provide for a delayed operation 01' the motor so that a scavenging action is continued in the combustion chamber after the fuel supply thereto has been cut oil. This operation or the motor relative to the operation of the pump. 8| serves to prevent any excess of fuel being present in the combustion chamber when heater operation is initiated.

-As was previously mentioned the motor 88 is a in Fig. l the bellows unit 81 is carried on a bracket 88 in a manner such that the movement of the diaphragms is additive relative to the actuating bar 88. In other words the movement of the bar is double the movement of each diaphragm 85.

In providing for'the operation of the heater at high altitudes the maximum speed of the motor 88 at the power available for its operation, the

capacity of the Ian 88, and the size of the inlet 88 at full open position are relatively determined so that sufllcient air and hence oxygen'i's fed to to the combustion chamber at the highest altitilde at which the heater is to operate. When this relation is determined the openings to the combustion chamber and the speed 01' the motor 88 are relatively and progressively decreased to a provide for the eflicient operation of the heater at all altitudes up to the highest desired altitude. In one embodiment of the invention the heater is adapted to be completely operated from a storage battery having a normal rating of about 24 volts. With the above described relation determined for a maximum altitude ofabout 50,000 Ieetfthe motor 84 and the fan 38 are of such sizes that the motor is too small to operate the fan 88 when the louvers 84 are wide. open at ground level. In other words, the fan is oversize relative to the motor for normal ground operation but is readily operated at the extreme altitude with the louvers in a wide open position.

Since the louvers are intended to be wide open only at the extreme altitude of 50,000 feet, a partially closed position of the louvers at ground level reduces the fan load so that it is operated by the motor to deliver an oxygen supply to the combustion chamber which is substantially equal to the supply of oxygen at the high altitude position when the louvers are in a wide open position. In the operation of the heater, therefore, as the to the mixing means 22 might result in a too rich mixture being supplied to'the combustion chamber II. To maintain a substantially uniform fuel mixture at all altitudes the rate of fuel in altitude the bellows unit 81 is expanded by the action of the spring 68 to progressively move the louvers 64 to a wide open position. As a result of the air becoming less dense with an increase in altitude the load on the motor produced by the fan decreases so that the motor increase in speed concurrently with the movement of the louvers to their open position. This progressive increase in the speed of the motor 34, concurrently with the change in the size of the inlet opening 39 as varied by the louvers 64 continues until the louvers are in their wide open position corresponding to the highest altitude at which the heater is adapted to operate with ground level eilicienecy. By virtue of the increase in the quantity of air supplied with an increase in altitude, compensation is made for the reduction in oxygen content with an increase in altitude so that the supplyof oiwgen at all altitudes is maintained substantially constant. Combustion conditions over the entire range of altitudes at which the heater is operated are thus retained substantially uniform.

If further compensation in controlling the air supplied to the combustion chamber I5 is required it .may be obtained by means of a voltage regulator ll carried on the housing end 24 having a regulating arm 80 operatively connected to the actuating member 66 for operation by the bellows unit 61. The voltage regulator or rheostat Ii functions to increase the power applied to the series motor 34 with an increase in altitude to augment the speeding up of the motor resulting from its being of series wound type. It is to be understood of course that this speed control may be utilized regardless of the type of motor used in the heater apparatus to provide for the necessary increase in the air supplied to the combustion chamber IS with an increase in altitude.

Since the speed of the motor 34 as controlled by the voltage regulator 1| might not be required until after some predetermined altitude, its operation may be delayed until such predetermined altitude is reached. Thus as shown in Fig. 2 the regulating arm 801s mounted for pivotal movement on a shaft 8| which also carries an arm 82 having a slot 83 therein for receiving a pin 84 mounted on a link 85 carried on the actuating bar 66. It is seen, therefore, that the arm 80 remains stationary until the lost motion in the pin and slot connection is taken up after a predetermined movement of the actuating arm 68 by the bellows unit 61.

At altitudes in the neighborhood of 50,000 feet it may be found necessary under some conditions of operation to change the rate of fuel supply to the conditioning means 22. As was hereinabove noted the fuel is supplied to the mixing means 22 by a pump 4| operated at a rate dependent upon the speed of the motor 34. At these high altitudes the quantity of fuel supplied lows unit 61' and an actuating member 86' which are constructed and operated in all respects similar to the bellows 8 1 and actuating bar 66 associated with the air supply inlet 38. The bar 66' is formed with a slot 12 adapted to receive a pin 13 carried at one end of a pivoted link member 14. The opposite end of the link member 14 is pivotally connected with a valve member I6 formed as a part of a valve unit 11 connected in the fuel supply line 44. The pin and slot connection 12-43 provides for a 10st motion between the bar 66' and the link 14, so that movement of the link I4 is not immediately responsive to the expansion of the bellows unit- 61. In other words, the supply of fuel to the mixing means 22 is not varied in response to atmospheric conditions until an altitude is reached at which the pin 13 is in driven engagement with the bar 66'. After this engagement takes place the air and fuel supplied to the combustion hamber is concurrently varied in response to the barometric pressures acting on the bellows unit '61. It is to be understood, of course, that under some conditions of operation the fuel may be varied concurrently-with the air over the complete range of altitudes at which the heater is to operate.

This control of the air and fuel results in combustion conditions in the heater being maintained substantially uniform at all altitudes to in turn provide for a substantially uniform generation of heat within the combustion chamber i5. Be-

, tity ofair circulated in the passage 29, as the altitude increases, is attained to an appreciable -extent by the speeding up of the motor 34 as the density of the air decreases. A further increase, however, is provided by controlling the air admitted into the mechanical compartment l2 at the inlet 41, thereof, by a damper means 60' similar in all respects in construction and operation to the damper means 60 associated with the air supply inlet 39. The louvers 64' are connected to the actuating member 66' so that the bellows 61' operates both the damper means 60 and the valve unit 11. In view of the description and operation of the bellows unit 81 and damper means 60 it is believed that a further description of the bellows 61 and damper 60' is unnecessary. It is seen, therefore, that both the air and fuel supplied for combustion and the air supplied to the passage 26 may be relatively varied by barometric pressure responsive means so as to maintain the over all operation of the heater substantially the same at all altitudes. It is to be understood of course that the operation of the voltage regulator II also controls the speed of the fan 32, the size of which relative to the motor 34, and inlet, 41 is determined in all respects similar to the selection of the fan 38 as was explained above. As described in Fig. 1 the air adcause of the rarifled atmosphere.

means I at the discharge end of the tail pipe 23 which is adapted to be operated concurrently In the present invention capacity when the air admitted thereto is closed 7 I louvers I03 operatively associated with the discharge end of the exhaust tail pipe 23 to control the flow of air through the combustion chamber. The inlet 38 to the fan 38 is of a fixed size and without any damper control means.

In the operation of this assembly the louvers I 03 are in a substantially closed-position when the heater is at ground level so that the load on the motor 34 is less than it would be if the fan were operated with the louvers in a full open position. The iouvers,-however, are opened a predetermined amount to permit a proper operation of the heater at ground level. As the altitude is increased the louvers I03 are progressively moved to a wide open position in response to the action of. the bellows unit 61 to allow an increased flow of air through the combustion chamber I5 due to the increased speed of operation of the fan 38 by the motor 34. In other words the outlet for the combustion chamber I5 is gradually opened with an increase in altitude so that more air is admitted to the combustion chamber at rarifled atmospheres to retain the oxygen supply thereto substantially uniform. The'rheostat 1| may -be connected with the actuating member I02 to control the operation of the motor-34 in the manner above described in connection with Fig. 1. It is to be understood of course that the damper means 60' associated with the inlet 41 to the circulating air -passage 28 and the valve unit 11 for varying the supply of fuel to the mixing means 22, may be used in all respects aspreviously explained for Fig. l.

-In the contro1 of the air supplied to the combustion chamber I5, as shown in Fig. 1, theexhaust tail pipe 23 is left entirely open. .It is apparent, of course, that in the operation of the heater at high altitudes a reduction in the come bustion chamber back pressure takes place be-' In other words the exhaust from the combustion chamber acts against a smaller pressure at high altitudes than is encountered at ground level. Since this'reduction in back pressure exists concurrently with -an increased speed 'in the operation of the fan 38 there is produced in the combustion chamber I5 an increased velocity headwith a decreased static pressure. Thus although a greater quantity of air is supplied to the combustion chamber I5, this air operates against a reduced pressure in the Some propeller type fans also have this As a result the load on the motor with the damper means 80 at the fan inlet 39, as shown in Fig. 6. The actuating member I02 for the damper means 15 and the actuating member 88 for the damper means 50 are operatively connected to opposite sides of a bellows uniti'I so as to be moved in opposite directions by the expansive movement thereof.

In the embodiment of Fig. 6 the damper means 60 and voltage regulator 'II are operated in all respects similar to their operation in Fig. 1. The damper means I5, however, is operated reversely to its operation in Fig.5 so that the louvers I03 are in a wide open position at ground level and are moved to a closing position with an increase in altitude. Thus the quantity of air supplied to the combustion chamber I5 is controlled by the damper means 80 while the damper means I5 opcrates to retain a substantially uniform operating or back pressure in the combustion chamber. There is thus provided an air control which maintains the supply of oxygen to the combustion chamber, and the static and velocity head in the combustion chamber substantially uniform over a complete range of altitudes. It is apparent of course that the damper means 50 for the heated air inlet 41 may also be used with the air control means of Fig. 6.

A further embodiment of the invention is shown in Fig. 7 formanually controllingv the air supplied to the heater over a range of altitudes. The damper means I05 for the air inlet 39 includes louvers I06 connected to an actuating bar IIl'l havin a rack'portion I08 at one end for engaging a pinion I08 carried on a shaft III. The opposite end of the bar I0! is pivotally connected to one arm of. a. bell crank II 2 pivoted on the housing III. The second arm of the bell crank I I2 is pivoted to an actuating bar II8 for damper means Ill havingqlouvers' II6.- The'damper means I I4 controls the passage of air through the inlet .41 for the heated airfpassage 28.

The shaft III has a pinion III thereon in 45 operative engagement with a gearsegment II8 carried on an indicator shaft II! for indicating mechanism designated generally as I2 I. An'indicator I25 mounted on the shaft I I8 is operatively associated with a dial face I22 having altitude indicationsther'eon. Rotation of the shaft II! to move the indicator I25 across the dial face I22 is accomplished by a handle portion I23. It isseen, therefore, that on rotation of the shaft I IS the actuator bars I01 and I I3 are concurrent 68 1y moved through the above described gear train' to operating positions corresponding to the altitude indicated by th indicator I25. Movements of the indicator I25 to a particular altitude indication are made in accordance with the altitude 60 readings as recorded on a usual type altimeter incombustion chamber with a resultant increase in velocity relative to its velocity at ground level,

Under some conditions ofoperation this velocity might attain proportions such that insufficient time is permitted to completely burn the combustible mixture within the combustion chamber I5. To prevent this condition and to provide for the operation of the heater with combustion chamber pressure conditions substantially the same at all altitudes there is provided a damper 70 I05 and III to corresponding positions providing strument (not shown) which is provided on the aircraft. Asshown in Fig. 7 the aircontrol for the heater is contemplated to start at altitudes above 20,000 feet. With an increase in altitude above 20,000 feet as recorded by the altimeter the operator of the aircraft moves the indicator I25 to indicate an altitude corresponding to the altituderecorded by the altimeter. This movement of the indicator I25 operates the damper means for a proper supply of air to the heater at the altitude shown by the indicator I25. It is to be understood of course that the rheostat II, and fuel. valve 11 may be 'operatively connected with 7 the actuator arms I 01 and I I3 t provide for thei vention provides a heater of internal combustion type which is adapted to operate over a wide range of altitudes with substantially uniform operating conditions. The control means for the combustion air and for the air to be heated are actuated in accordance with the altitudes at which the heater is being operated in response to the barometric pressures at such altitudes by simple bellows means so that the complete air I control assembly is very compact and readily applied to a plurality of heaters of different types. The control of the air and hence of the oxygen supplied to the heater is accomplished by the cooperating action of a plurality of air compensating means. In other words the quantity of air supplied is varied by the action of a series motor, by varying the power applied to the motor, and by varying the air admitted to the air supply fans by means of adjustable inlets and outlets therefor, with all of these air control means being automatically operated in response to the varying barometric pressures at different altitudes. It is to be understood of course that any combination of these compensating means, or any one of these compensating means, may be utilized under various applications to provide for a constant supply of oxygen to a heater of internal combustion type over a wide range of altitudes.

It is to be understood further that although the present invention has been described and illustrated with respect to several preferred embodiments thereof that it is not to be $0 limited since modifications andalterations can be made therein which are within the full intended scope of this invention as defined in the appended claims.

I claim:

1. In aircraft heating apparatus adapted to be installed aboard an aircraft to heat the craft while in flight at varying altitudes, means defining a combustion chamber, means for delivering fuel to said combustion chamber, means supplying air for combustion to said combustion chamber including air moving means having an inlet with an adjustable opening, an electrical motor for driving said-air moving means, altitude i'einstalled aboard an aircraft to heat the craft while 'in flight at varying altitudes, means defining a combustion chamber, means for delivering fuel to said combustion chamber, means for feeding combustion air to said combustion chamher having an inlet opening, and the combination of means providing for an increase in volume rate of air flow in correspondence with an increase in altitude including adjustable means at said inlet opening for controlling the passa e of air therethrough, which comprises a variable speed electric motor for operating said air feeding means, a circuit for said motor including means for controlling the supply of electrical energy to said motor, and altitude responsive means operatively connectedwith said adjustable means and control means to concurrently operate the same.

3. In aircraft heating apparatus adapted to be 1 installed aboard an aircraft to heat the craft while in flight at varying altitudes, means delining a combustion chamber, means for delivering fuel to said combustion chamber, and the combination of means providing for an increase in the supp y of combustion air to said combustion chamber with an increase in altitude including air moving means, a series motor for operating said air moving means, whereby the density of the air moved by said air moving means is reduced as the altitude increases whereby the speed ofsaid motor increases, a circuit for said motor including adjustable means for varying the power applied thereto, and altitude responsive means for operating said adjustable means to increase the power applied to said motor with an increase in altitude.

4. In aircraft heating apparatus adapted to be installed aboard an aircraft to heat the craft while in flight at varying altitudes, means defining a combustion chamber, means for delivering fuel to said combustion chamber, air moving means for supplying air to said combustion chamber having an inlet opening, adjustable means for' varying the size of said opening, an electric motor for driving said air moving means, a circuit for said motor including a source of energy of a predetermined value, means for varying the power applied to said motor, said power varying means being adjusted so that said motor is capable of operating said air moving means at substantially ground level only when said adjustable means is at a position providing for a substantially minimum size of said inlet opening, and means responsive to atmospheric pressures for concurrently operating said adjustable means and power varying means so that the size of said opening and the power applied on said motor are increased with an increase in altitude.

5. In heater apparatus adapted to operate on an aircraft in flight over a wide range of altitudes varying in pressure and oxygen content, means defining a combustion chamber having inlet and outlet portions, air moving means for supplyin air to said combustion chamber, means for supplying fuel to said combustion chamber, damper means operatively associated with one of said two portions to control the admission of air into said combustion chamber, a variable speedelectric motor for operating said air moving means including means for controlling the supply of energy thereto, valve means for varying the supply of fuel to said combustion chamber, and means responsive to the atmospheric pressures over said range of altitudes to operate said damper means, said energy supply means, and said valve means for maintaining a substantially uniform ratio of oxygen to fuel for burning in said combustion chamber.

6. In aircraft heater apparatus for heating purposes while the aircraft is in flight and comprising a heat generating u'nit provided with a combustion chamber and means defining a passage for air to be heated arranged in thermal relation with said combustion chamber and air moving means for circulating air through said passage; apparatus providing for the generation of heat in the unit and for a substantially uniform amount of heat being carried away from ing means and said air feeding means at increasing altitudes tends to increase the speed of operation of said motor with an increase in altitude, an energizing circuit for said motor includ-, ing adjustable means for varying the power delivered by said motor, and means responsive to atmospheric pressures acting on said adjustable means to increase the power delivered by said motor with an increase in altitude.

7. In aircraft heating apparatus adapted to be installed aboard an aircraft to heat the craft while in flight at varying altitudes, means deflning a combustion chamber having an exhaust openin means defining an air heating chamber having an inlet opening and arranged in heat exchange relationship with said combustion chamber, means having an air inlet opening from which air is de-- -ing the characteristic of speeding up as the density of the air moved by said air moving means is decreased at increasing altitudes, whereby the volume of air moved by said air moving means tends to increase with increasing altitude of operation of said craft, adjustable damper means respectively provided at said openings to control the volume of air flow therethrough, a first altitude responsive device for controlling the damper means at said combustion chamber air inlet and exhaust openings to increase the volume rate of air delivery to said combustion chamber with increasing altitud of aircraft operation, a second altitude responsive device for controlling the damper means at said air heating chamber inlet to increase the volume rate of air flow through said heating chamber with increasing altitude of an air heating chamber arranged in heat exchange relationship with said combustion chamber, air moving means for delivering air to said air heating chamber, altitude responsive means for changing the volume rate of air delivery to said heating chamber in the same sense with changes in the altitude at which the-aircraft is operated, means controlled by said altitude responsive means for decreasing the rate of fuel delivery to said combustion chamber as the altitude of aircraft operation increases, and means for preventing said last-named means from operating until a predetermined altitude of aircraft operation is reached.

10. In aircraft heating apparatus adapted to be installed aboard an aircraft to .heat the craft while in flight at varying altitudes, means defining a combustion chamber, means for delivering fuel to said combustion chamber, means including a variable speed electric motor for delivering an adequate mass of combustion air to said combustion chamber until a predetermined altitude of aircraft operation is attained, altitude responsive means operative automatically to increase the energization of said motor as the altitude of operation of the aircraft is increased, thereby to increase the volume rate of air delivered to said combustion chamber as the altitude of operation of aircraft is increased, and means for preventing said last-named means from operating until said predetermined altitude of operation of the aircraft is reached.

11. In aircraft heating apparatus adapted to be installed aboard an aircraft to heat the craft while in flight at varying altitudes, means defining a combustion chamber, means for delivering fuel to said combustion chamber, air moving means for supplying air to said combustion chamber and having an inlet opening, a motor for operating said air moving means, adjustable means for varying the size of said inlet opening, means for supplying said motor with a minimum of energy for moving the air furnished by said inlet openings at the air densities at ground level when ation is increased above a predetermined height.

8. In aircraft heating apparatus adapted to be installed aboard an aircraft to heat the craft while in flight at varying altitudes, means deiining a combustion chamber, means for delivering combustion air to said combustion chamber at a mass rate which tends to decrease with increasing altitude of aircraft operation, adjustable fuel feed means for delivering fuel to said combustion chamber, means deilningan air heating chamber arranged in heat exchange relationship with said combustion chamber. air moving means for deliv-' ering air to said air heating chamber, altitude responsive means for changing the volume rate of air, delivery to said heating chamber in the same sense with changes in the altitude at which thefuel to said combustion chamber, means defining said inletopening is of substantially minimum size and the air flow is correspondingly small, and means responsive to changes of atmospheric pressure for increasing the size of said inlet opening and for increasing the supp y of energy to said motor with an increase of altitude, whereby the reduction in power required to move the less dense air at said increased altitudes together with the increased power applied to said air moving means produces a greater volume rate of air flow .to said combustion chamber.

- opening for controlling the passage of air therethrough, a variable speed electric motor for operating said air feeding means, a circuit for said motor including means for controlling the supply of electrical energy to said motor, and altitude responsive means operatively connected with said adjustable means and control means to' concur. rently operate the same.

mass 3. noaraooss. 

